Embedding material for electrical heating units.



I06. COMPOSITIONS,

COATING OR PLASTIC.

Cross Reierenie Examiner D TE PATENT OFFICE 1 No Drawing.

sAITIIEI. r. wILBUEfoE PITTsB GH, PENNS LVANIA, Assrelvon, Er MESNE ASSIGN- MENTS, T0 H LIoN ELECTRIC COMPANY, A coEronATIoN or NEW JERSEY.

"'EMBED'DING MATERIAL FOR ELECTRICAL HEATING UNITS.

To all whom it may concern:

. Be it known that I, SAMUEL P. WILBUR, ofthe city of Pittsburgh, county of Allegheny, and State of Pennsylvania, have invented-a new anduseful Improvementin Embedding Material for Electrical Heating Units, of which the following'is a full, clear,

and exact description.

My invention relates to improvements in embedding materials for heating units, and the objecteof my invention is to produce an embedding material in which the heating unit may be embedded, and. which will serve to protect the heating unit against breakage or excessive oxidation, and will also serve as a good distributing medium for the heat generated by the unit.

My invention while serving for an embedding material, is especially adapted as an embedding material for high resistance heating units, whichbecause of their high resistance, likewise have a high temperature when a current is passed through them.

Another object of my invention is to produce an embedding material which while of high electrical resistance is a good heat conductorl and can be readily shaped around the heating unit to be embedded, and infact can be given any desired shape or configuration.

Still another object of my invention is to produce an embedding material which is inexpensive, and While having the characteristics above mentioned, has such a coefiioient of expansion that it is not affected by sudden temperature changes, and will not crack or disintegrate under rapid changes of temperature.

I have found that owdered carborundum when mixed with a suifable binder, Torms an embedding material of the kind referred to, and in using this material I preferably use as a binder commercial silicate of soda. with water enough to dampen e mass so that mrticles will adhere and permit the shaping of the mass. The whole may be placed in a suitable mold or die and under sufiicient ressure to hold it together firmly and to give 1 e desired shape. Instead of shaping under pressure, the embedding material may be made plastic and applied as a paste over the filament or heating unit to serve as an embedding material. The heating unit is of course placed in the mass so as to be embedded, and with its ends ar- Specification of Letters Patent.

PatentedJan. 19, 1915.

Application filed November 13,1911. Serial m. 660,121. l g ,e.

ranged for suitable electric connection. TVhen shaped, the mass is baked at a low temperature, and then brought to a high temperature which forms it into a hard durable mass. The embedding material as stated can be used with very high resistance heating units, even though when heated they have a temperature of-high incan descence, and I have used iton heating units running as high as; 1500 degrees C. when heated. The reasonfor this is that the em bedding material is such a good conductor of heat thatit carries away the heat from the unit so rapidly that the embedding ma- 'terial itself is not affected. Silicate of soda is a common binding material for analogous compositions, and serves perfectly the purpose intended, but other binders may .be used such for instance: as gum arabic, or any 'of;tl 1e sugar compounds.

. I can vary the conductivity of the embedding material, and to render it less conductive can mix with it any desired percentage of. alumina, silica, or other poor electrical conductors at high temperature. This does not affect the general efiiciency of the embedding materiaL- It'will be'radily seen that the embedding material can be given suflicient mass and suitable shape to adapt it for a heating unit in sad irons, soldering irons, cooking devices, and other apparatus, and when the current is passed through the heating unit proper, the embedding material becomes a heat radiator and Will itself stand a comparatively high temperature.

In carrying out the invention tlie better way is to first coat the heating unit with a fine grade of carborundum so as to make an air tight seal, and then cover the unit and its coating with the coarser material having better drying qualities.

It will be understood that a high resistance and consequently high temperature heating unit, especially in filament form, is not adapted to a great many heating purposes, but by embedding the heating unit in material of the kind stated, I- get a substantially large body, that is large in relation to the heating unit, which makes a good distributor of heat at a lower temperature than that of the actual unit, and

which I use, while readilyadapting itself to any necessary shaping, affords an elec- V 1. The combination with a high resistanceelectrical heating unit, of an embedding material inclosing the heating unit, and alfording electric insulation therefor at ordinary commercial voltages and providing a radiating body much larger than the body of the heating unit, said embedding material consisting-of finely divided refractory carbid and a binder.

2. The combination with a heating unit in filament form, of an embedding material 'inclosing the filament and forming a substantial heat radiating body much larger than the filament, said material consisting of finely divided refractory carbid and a Y-binder-said material afiording'electric insulation at usual commercial voltages.

3. The combination with an electric heating unit of high resistance, of an embedding material for said unit, comprising powdered refractory carbid and a binder, the mass with the heating unit therein being suitably shaped andba'ked, and forming a relatively bulky .heat radiating body said embedding material affording electric insulation at ordinary commercial voltages.

4. The combination with an electric heating unit of high resistance, of an embedding material for the'same, comprising a finely divided refractory carbid and a binder, the material being plastic when shaped and hard after drying, and forming a relatively large heat radiating body said embedding material affording electric insulation at or- 40 dlnary commercial voltages.

- V 5. The combination with an electric heating unit, of an embedding material therefor consisting of powdered carborundum and a hinder, the embedding material being bulky as compared with the heating unlt, and

forming a substantial heat radiating body said embedding material affording electric insulation at ordinary commercial voltages.

6. A heat unit consisting of an electrical '50 conductor anda covering enveloping the active part of the conductor, 'said covering consisting of carbid, silicate of soda and water. t 7. A. heat unit consisting of an electrical conductor and a covering enveloping the active part of the conductor, said covering "consisting of finely divided carbid, silicate of soda and a liquid.

8. A heat unit consisting of a Wound elec- 6O trical conductor and a covering of high electric resistance but high heat conductivity, said covering containing finely divided carbid and a binder consisting of silicate of soda and a liquid.

SAMUEL P.-WILBUR. Witnesses'i R. W. BAKER, WARREN B. HUTCHINSON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, TD. 0. 

